Motion picture equipment currently used in theaters utilizes complex film handling systems which require the film to travel considerable distances from the supply reel to the projector and back to the take-up reel. The film also passes over a number of guiding or film transport rollers and through feed controls also utilizing such rollers. A considerable amount of static electricity often builds up on the the film, especially during dry conditions, causing the film to stick and/or bunch. This requires the projectionist to stop and rethread the film, often causing unrest among the theater patrons. Various means have been devised to remove the static electricity and thereby to eliminate this problem.
U.S. Pat. No. 3,585,446 to McKee disclosed a conducting system to dissipate static electric charges that build up on motion picture reels. A plastic spindle covered with a conductive coating was secured to the metal shaft supporting the reel. The coating was in contact with both metal flanges of the reel and with the shaft, enabling the charges to migrate from the reel to the coating and then to the shaft and finally to the projector where the charges were dissipated. The projector preferably was grounded.
Whitmore, in U.S. Pat. No. 3,611,028 disclosed a metal roller with metal stub axles which were supported by the grounded frame of a conveyor system. The metal roller, used to guide a web, particularly photographic film, was covered with a layer of an elastomeric plastic which prevented charges on the metal roller from being imparted to the film.
Rollers, composed of non-magnetic stainless steel, in contact with brushes for grounding, were used in a complex web device color copier photoelectrophoretic imaging machine as taught by Hermanson in U.S. Pat. No. 4,049,343. A conductive web surface, in contact with a roller, was grounded by another set of brushes.
Geyken, in U.S. Pat. No. 4,392,177 described four embodiments of rollers for use with webs, sheets or strips of flexible radiation sensitive material such as X-ray film. The rollers were constructed of a plastic material with imbedded metal particles surrounding a metal shaft that extended beyond the ends of the plastic material. The metal shaft was grounded.
In U.S. Pat. No. 4,737,809, Konno taught a camera fitted with two guide rollers in pressure contact with the film. Both guide rollers were in further contact with springs that contacted grounding parts of the camera to remove static charges generated on the film under dry conditions.
Another roller for use with lengths of polymeric film was taught by Ko in U.S. Pat. No. 5,216,571. A metallic conducting core having a metal shaft at each end was surrounded by a non-conducting material having a helical groove cut into it. A conducting wire placed in the groove was in contact with a grounded bearing located at the end of one shaft. The wire had conducting needles radiating outwardly along its length.
Means to remove static electricity from photographic film was taught by Oosaka in U.S. Pat. No. 5,625,468. Four embodiments were described: a metal brush that contacted the perforated edge of the film; arms in contact with conducting members that made contact with each side of the film; conductive pins that contacted the edge of the film; and conductive flanges that contacted the edge of the film. All of these contact means were conductors and all were grounded.
All of the prior art devices for the prevention of sticking or bunching of flexible films or webs depended on the removal of the static electricity from the films or webs through one or another form of ground. There is a need for a simple means to prevent such sticking or bunching of films that can be used with a variety of film handling methods and apparatuses without the additional requirement of a ground.